rhetorical principles should be observed in argumentation more rigidly
than elsewhere, for in the case of narration, description, or
exposition, the reader or hearer, in an endeavor to derive pleasure or
profit, is seeking the author, while in argumentation it is the author
who is trying to force his ideas upon the audience. Hence an argument
must contain nothing crude or repulsive, but must be attractive in
every detail. In the second place, any composition that attempts to
alter beliefs must deal with reasons, and the science of reasoning is
logic. There is no need for the student of argumentation to make an
exhaustive study of this science, for the good arguer is not obliged
to know all the different ways the mind may work; he must, however,
know how it should work in order to produce trustworthy results, and
to the extent of teaching correct reasoning, argumentation includes
logic. In the third place, a study of the emotions belongs to
argumentation. According to the definition, argumentation aims both at
presenting truth and compelling action. As action depends to a great
extent upon man's emotions, the way to arouse his feelings and
passions is a fundamental principle of this art. Argumentation, then,
which is commonly classified as the fourth division of rhetoric,
consists of two fundamental elements. The part that is based upon
logic and depends for its effectiveness upon pure reasoning is called
_conviction_; the part that consists of an emotional appeal to
the people addressed is called _persuasion_. If the only purpose
of argumentation were to demonstrate the truth or falsity of a
hypothesis, conviction alone would be sufficient. But its purpose is
greater than this: it aims both (1) to convince men that certain ideas
are true, and also (2) to persuade them to act in accordance with the
truth presented. Neither conviction nor persuasion can with safety be
omitted. An appeal to the intellect alone may demonstrate principles
that cannot be refuted; it may prove beyond a doubt that certain